Silicon sand extraction refers to the process of removing the main impurities in silica sand to obtain refined silica sand or high purity silica sand. The extraction of Silicon sand generally adopts physical beneficiation or chemical method, and the purification of silicon sand through beneficiation method is the lower-cost crude purification method. Compared with conventional beneficiation methods, chemical purification has shortcomings such as high cost and complicated operation. So let's take a look at the physical separation of Silicon sand.
01Why Should Silica Sand Impurity Be Removed?
Refined silica sand is an important industrial mineral raw material, which is widely used in glass, plate, filter material, etc. And the raw ore of silicon sand can meet the demand of industrial sand only after beneficiation. High purity silica sand, as a high-tech sand, needs to be further purified on the basis of refined silica sand.
02Separation Process
The main impurity minerals in silica sand are chlorite, feldspar, mica, iron-containing impurities and clay minerals, etc. The main criterion for judging the purity of silica sand is the content of iron and aluminum. Therefore, the purification of silica sand is to remove the iron and aluminum impurities in the ore.
1. Removing Iron from Silica Sand
There are five forms of iron in silica sand. Different forms of beneficiation, such as scrubbing, gravity separation, magnetic separation, flotation and acid leaching, are required for iron impurities in different retention states.
(1) Iron Adheres to the Surface of Silica Particles in the Form of Iron Oxide Film
The iron impurities attached to the surface of silicon particles in the form of iron oxide film can be removed by scrubbing and pickling. Scrubbing is divided into mechanical scrubbing and ultrasonic scrubbing. Mechanical scrubbing is widely used in production practice due to its simple equipment and low cost.
(2) Iron in Clay or Feldspar in the Form of Fine Particle Size
Feldspars or iron-bearing clays that are prone to mud are usually removed by de-mudging. Since the hardness of silica in raw ore is higher than that of iron-bearing clay or feldspar, the iron-bearing clay or feldspar is more easily muddied, and the grade of iron impurities becomes larger as the grain size decreases. Therefore ,de-mudding is effective in removing such iron minerals contained in clay or feldspar.
(3) Iron Is Disseminated or Lenticular In The Silicon Particles
Iron impurities present in the interior of the silicon particles in the form of dip or lens, generally used to removed by froth flotation .
(4) Iron As A Solid Solution Exists In Silicon
For iron impurities present in the silicon crystal in solid solution, the silicon crystal must first be opened and then removed by acid leaching.
(5) Secondary Iron Is Mixed Into the Crushing and Grinding Process
For iron mineral and secondary iron with high density or magnetic properties, gravity separation and magnetic separation can be used to remove.
2. Removing Aluminum from Silica Sand
Aluminum impurities exist in silica ore in the form of aluminum-containing minerals such as mica, clay and feldspar. and in the case of clay minerals, they are generally removed by desliming. Because feldspar and silicon physical properties are similar, gravity separation and magnetic separation are difficult to separate feldspar and silicon, flotation is the most effective way to separate the two. The Acid flotation of feldspar is widely used in industry because of its matureness .
Acid flotation of feldspar is the preferential flotation of feldspar at a pH of about 2 to 3. using a mixed collector of anion and cation. The complexes formed by anion and cation are more surface active than single collector, and the recovery of flotation is higher when there is more cationic collectors in the mixed collector, otherwise, flotation is inhibited.
03
1. Grinding and Scrubbing Equipment
(1) Grinding is the process of reducing the size of minerals under the action of mechanical force and dissociating the useful and useless components symbiotic in minerals. In the process of grinding, silica ore will be in contact with the mill, and impurities will inevitably be introduced. Therefore, the grinding material itself can be used as the grinding medium, which can greatly reduce the pollution of silica ore by the mill medium.
(2) Scrubbing and desliming after the grinding process. The scrubbing is to scrub the particles and disperse and dissociate the mud material, which can effectively remove the mud glued to the mineral surface. This is very effective in removing the thin film iron and muddy impurity minerals from the surface of silica ore particles.
2. Classification Equipment
Classification is the process of sorting mineral particles according to their specific gravity, size and shape. Classification can also play the role of desliming to reduce iron content. Because the hardness of iron-containing minerals is lower than that of silica sand, under the same grinding conditions, the minerals with lower hardness will reach the grinding effect first.
Silica sand classification equipment mainly includes: vibrating screen, classifier, hydrocyclone and so on.
3. Flotation Equipment
Flotation is based on the difference in wettability of the silica sand surface, natural or modified, and the tendency of silica sand particles to bind with air bubbles. The scraper scrapes out the foam attached to the silica sand particles, while the phosphorus-containing, iron-containing minerals or mica and feldspar minerals symbiotic with silica ore are still suspended in the slurry, so that the silica sand minerals and harmful minerals can be separated, and finally achieve the purpose of mineral separation.In addition, flotation can also be used to remove secondary iron mixed in during crushing and grinding.
4. Gravity Separation Equipment
Gravity beneficiation takes advantage of differences in the density and particle size of minerals. With the help of the medium fluid and various mechanical forces of the combined action of the media to create suitable conditions for loose stratification and separation, so as to obtain different density or different particle size products of the process.
Generally for iron-containing heavy minerals, as well as crushing and grinding mixed with secondary iron ore beneficiation. Commonly used equipment is mainly spiral chute, shaking table and so on.
04To Wrap Up
The above is related to silica sand extraction. The impurity endowment form in silica sand is more complex and diverse, only according to the impurities in the siliceous raw materials in the endowment state to select the appropriate beneficiation methods and processes to achieve better results. It is recommended to have a more comprehensive understanding of the silica sand itself in the selection process and equipment, combined with the nature of the ore of silica sand, investment budget, plant conditions, etc. Through mineral processing test report targeted selection of a single or joint process, in order to strive for ideal technical and economic benefits.
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